Okay, so here's the general situation:

The party has started out with a veteran, fairly radical inquisitor by the name of Kirkman. He's been very hands off with the PCs so far, as in just giving them missions and expecting them to get on with it.

To be fair, their missions so far:

1) Investigate a minor food riot (turned out to be a cult of a Daemon Prince who was killed centuries ago and is apparently returning).

2) Head over to the Inquisitorial archive in a hive city, ask for records on said Demon Prince, then meet up with the Inquisitor (the records were being transferred off-world for another inquisitor and the transport was shot down. Cue 3-day trek through Ork-infested jungle to the crash site and discovery of a Heritech and a Tyranid Vanguard organism).

This then gives the PCs the chance to choose between 3 assignments: Investigate the Heritech, Keep working on the Daemon Prince case or deal with the 'nids. They decided on the Heritech, the Inquisitor set a different group to deal with the Daemon Prince, while Kirkman himself is leading the charge against the 'nids.

Now the mission here is infiltration, which is good because the group leader is a Tech Priest and the cult is the Logicians. I plan on using this to shake his faith and hopefully get some good RP out of him. The reason they had an agent hanging around the crash site was to pilfer some data on a group called the Immaculate Hand, a Slaanesh cult that's taken root in the lower hive and who's influence the Logicians are combating. Meanwhile, the Tech Priest's old gang (their first lead) has been taken over by the Dark Eldar who're basically using them as middle men for trading and slave acquisition (Minor Kabal, trying to get a reliable source of resources between raids), and there are also Enslavers in the area, which is sure to be very healthy for the group's (Xenos, because who'd expect that the group with a Xenos is working for the inquisition?) Unsanctioned Psyker. Oh, and the scum is looking like they might be amenable to some good old fashioned corruption by the ruinous powers (the Player gained Korne's favor by firing a flamer-type weapon indiscriminately into melee, being rewarded with 10 corruption points and the Frenzy talent for free. The Immaculate hand would prefer to recruit her for Slaanesh, which the player has no problem with as the character is supposed to be a seductress-type anyway.)

Kirkman specified in the mission briefing that if they have to perform heresy in the name of maintaining their cover then it is regrettable, but necessary for the mission. They'll have to justify everything to him afterwards and possibly perform penance, but it's better than having the cult scatter and rebuild after being dealt with.

So, the plan is that when the group is on the verge of success, they get recalled. Kirkman has been killed in battle, and as a result there's a new Inquisitor in town who's recalling all acolyte cells to consolidate and review Kirkman's operations. While Kirkman was a veteran radical, this new Inquisitor is brand new and a very strict Puritan.

So, what I'm asking advice on is what background would best suit this new Inquisitor. I'm toying with the idea of a Sister of Battle or someone of that fanatical ilk. Whoever it is they have to be an immediately obvious and serious problem for the group beyond merely messing up their operation (though not irrecoverably, provided they ignore their new boss and head back to work after finding out the new situation).

Thoughts and suggestions?